UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WSG 131
Date Signed: October 8, 1999
MEMORANDUM
Subject: Issues in Potable Reuse
From: William R. Diamond, Director
Implementation and Assistance Division
To: Water Division Directors
Regions I-X
This memorandum is prompted by two reasons. Some regions have expressed an interest
in Headquarter's position on the reuse of treated municipal wastewater for the purpose of
augmenting drinking water supplies. In addition, prolonged drought events in recent years may
be prompting some utilities to look at alternative supplies including reuse of highly treated
wastewater effluents.
As water supplies become more scarce and demand keeps growing, more and more
utilities are turning highly treated wastewater effluents as a source of augmenting potable water
supplies. Major water reuse water projects involving indirect potable reuse can be found in
California, Texas and Florida and several states have promulgated regulations to govern these
projects along with other water reuse practices (see attached copy of Guidelines for Water
Reuse" EPA/625/R-92-004 published in September 1992, for summary information on these
requirements.) In 1998, the National Research Council (NRC) of the National Academy of
Sciences published a report entitled "Issues in Potable Reuse. " The report presented the results
of an extensive study of the practice and concluded that "planned indirect potable reuse is a
viable application of reclaimed water - but only when there is careful, thorough, project-specific
assessment that includes contaminant monitoring, health and safety testing and system reliability
evaluation." We support this conclusion and believe that in areas across the country
experiencing water supply problems, options involving indirect potable water reuse should be
explored in combination with water conservation which is mandated by the Safe Drinking Water
Act.
The NRC report raises some issues with indirect potable water reuse but points out that
similar concerns apply to the safety of potable water from conventional sources, particularly the
large number of sources exposed to sewage contamination which could be considered unplanned
potable reuse. The report notes more than two dozen major utilities serving populations from
25,000 to two million people, use water firm rivers that receive wastewater discharges amounting
to more than 50% of the stream flow during low flow conditions; large cities such as
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WSG 131
Philadelphia, Cincinnati and New Orleans, drawing water from the Delaware, Ohio and
Mississippi Rivers, respectively are effectively practicing indirect potable water reuse.
Indirect potable water reuse projects must be designed to provide assurances of safety.
Projects must take into consideration the contaminants which may be present in reclaimed water
in greater concentration than in natural waters. We note however, that most of the contaminants
which the NCR report cites as a concern for reuse projects are covered by recently promulgated
drinking water regulations: giardia, cryptosporidium, disinfection by-products, or are included in
the candidate contaminant list for future drinking water regulations. The NRC report provides
extensive guidelines for microbiological, chemical, toxicological and epidemiological studies as
well as monitoring programs, risk assessments and system reliability assessments. These
guidelines can be used to tailor an assessments of reuse projects which will vary from project to
project depending on the composition of the source water, and supplement the information
provided in the EPA "Guidelines for Water Reuse" document.
In conclusion, the safety of any given project is a function of the nature of the
wastewater, the extent to which it is treated, the characteristics of the water supply reservoir or
aquifer in which the water will reside, and the length of residence in the environment.
Therefore, each project must be examined on a case-by-case basis and a detailed assessment in
necessary for each project. The ultimate decision regarding the potential for employing indirect
potable reuse must be made at the local level.
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